United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #:  9611130283                                                  
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                                             October 23, 1996

MEMORANDUM TO:      Walter Haass, Sr. Reactor Engineer
                    Quality Assurance and Maintenance Branch
                    Division of Reactor Controls and Human F
                    Office of Nuclear Reactor Regulation

THRU:               Michael C. Modes, Branch Chief
                    Civil, Mechanical and Materials Branch
                    Region I, Division of Reactor Safety

FROM:               Michael McBrearty, Reactor Engineer
                    Civil, Mechanical and Materials Engineering Branch
                    Region I, Division of Reactor Safety

                    OIL HEAT EXCHANGER

During an inspection at Limerick last month, I spoke with you about a
potential Part 21 involving the design of the EDG lube oil heat exchanger
at Limerick.  At that time, Limerick was developing a letter to Coltec,
the EDG manufacturer who procured the lube oil heat exchanger as part of
the EDG system, requesting that Coltec perform a Part 21 evaluation.  You
asked me to get a copy of the letter and forward it to you, so that NRR
could evaluate the Part 21 aspects, and take any action needed to notify
other utilities that may be affected.  Limerick just issued the letter
and I have attached of copy.

Attachment: As stated

J.  Wiggins, DRS
S.  Black, NRR
M.  Modes, DRS
A.  Lohmeier, DRS
N.  Perry, SRI - Limerick
W.  Pasciak, DRP

                                             Nuclear Engineering Division

PECO NUCLEAR                                 PECO Energy Company
A Unit of PECO Energy                        965 Chesterbrook Blvd.
                                             Wayne, PA 19087-5691

Mr. T.M. Stevenson            June 10, 1996
Coltec Industries/FMED
701 White Avenue
Beloit, WI 53511

     Subject:  Limerick Generating Station, Units 1 &2 
               Emergency Diesel Generator Lubricating Oil Cooler 
               Request for 10CFR21 Evaluation

Dear Ted:

During work associated with the development of our EDG heat exchanger
performance monitoring program in response to USNRC Generic Letter 89-13,
our consultants from Stone & Webster/Boston determined that the Limerick
EDG lubricating oil coolers were undersized relative to the design
conditions reported on the heat exchanger data sheet.  The purpose of
this letter is to alert you to this matter, explain how this conclusion
has been reached, and request that you evaluate the situation for 10CFR21
reportability since we understand that "lo-fin" tubes similar to those at
Limerick may have been used in the lubricating oil coolers for Coltec
EDG's at other installations.

Attachment 1 is a copy of Bechtel's lubricating oil heat exchanger data
sheet 8031-M-71-DS-17.  Our records indicate that the sheet was completed
by Coltec during EDG design and manufacture and submitted to Bechtel as a
part of the purchase contract.  The data sheet provides the design
conditions for the heat exchanger and specifies a tube-side fouling
factor of 0.002.  When our consultant input the heat exchanger geometry
and the design conditions into Heat Transfer Research Inc.'s (HTRI) Shell
& Tube heat exchanger modelling program ST-5, Mod 0.50-1.30, using the
oil-side heat transfer rate of 83.2 BTU/(hr ft**2 degrees F) provided by
the heat exchanger manufacturer for SAE 30 oil, and the specified tube-
side fouling factor of 0.002, he found that a 22.8% undersurfaced heat
exchanger was actually delivered.  This is shown on pages 1 and 2,
respectively, of Attachment 2.

The tubes on this heat exchanger are Wolverine "lo-fin" tubes, 19
fins/inch, similar to Wolverine's Catalog No.  60-195049 except
fabricated of 90-10 Cu-Ni alloy.  The tube OD-to-ID area ratio is 3.62. 
In shelf-and-tube heat exchanger design, the individual factors which
comprise the total resistance to heat transfer must be referenced to
either the inside or outside surface of the tube.  If it is referenced to
the outside tube surface, the specified tubeside (inside) fouling factor
of 0.002 becomes 0.002 x 3.62 = 0.00724.  (Similarly, the 0.002 fouling
factor would be used unmodified if the reference surface was the inside
of the tube.) Our consultant suspects that the 0.002 fouling factor was
applied unmodified to the outside

Mr. T.M. Stevenson
Page 2
May 31, 1996

surface.  This would have been done during design by dividing the
specified tube-side fouling factor by 3.62 (rather than multiplying) to
yield 0.00055, and then applying it to the inside.

This case was run on the HTRI program and corroboration of this suspicion
obtained to within 0.461%.  This is shown on Attachment 3.

The use of a 0.00055 tube-side fouling factor is consistent with accepted
power plant design practice; however, its substitution for the specified
0.002 fouling factor reduces the amount of fouling margin and mandates
more frequent cleaning and testing of the heat exchangers in order to
maintain EDG operability.  For the Limerick design, sufficient margin is
available in the calculated post-accident temperatures of the Emergency
Service Water (ESW) system, in the post-accident loading (which is below
the continuous rating), and in the seasonal variation of ambient
temperatures such that precise scheduling of the cleanings will allow
Limerick to maintain EDG operability.

Please inform us of the results of your analysis and whether you concur
with the findings of our consultant.  Should your conclusions differ,
please provide us with the detailed technical bases for how your
conclusions were reached.  Should you have any questions regarding this
letter, please do not Hesitate to contact William McFarland of my staff
at 610-640-6465.

                              Very truly yours,

                              John B. Cotton
                              Director, Nuclear
                              Engineering Division
Attachments (3)

WJM/wjm a:\052996

Copy to:  N. Perry            USNRC Limerick Senior Resident Inspector
          C.F. Andreone       SWEC
          J.B. Cotton         63B-3
          R.J. Croke          SWEC
          L.J. Fusegni        SWEC
          M.P. Gallagher      LGS SSB 3-1
          G.H. Gellrich       63B-3
          J.P. Grimes         LGS SSB 3-1
          G.H. Hunger         62A-1
          T.B. Madden         SWEC
          W.J. McFarland      63B-3
          J.B. McLaughlin     LGS SSB 3-1
          V.M. Nilekani       63B-3
          W.J. Reilly LGS     SSB 3-1
          R.D. Weingard       LGS SSB 3-1
          File/DCC            Doctype = 231

Attachment 1

Bechtel Heat Exchanger Data Sheet

Table  "Lube Oil HEAT EXCHANGER DATA SHEET" omitted.

Attachment 2

Heat Exchanger Analysis
0.002 Tube-side Fouling Factor

Attachment 2 page 1 "ITT STANDARD" omitted.

Attachment 2 page 2  "HTRI ST-5 Mod. 0.50-1.30" omitted.

Attachment 3

Heat Exchanger Analysis
0.000555 Tube-side Fouling Factor

Attachment "HTRI ST-5 Mod. 0.50-1.30" omitted.

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